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Streptococcus pyogenes Gram Stain

Gram stain done on S. pyogenes showing the characteristic long G+ streptococcus chains. Culture grown on blood agar for 48 hrs at 37 degree’s C. Read More

Mycobacterium smegmatis Acid Fast Stain

Acid Fast stain done on a mix of Staphylococcus aureus and Mycobacterium smegmatis. Carbol fuchsin was applied to the smear and set over a steaming water bath for 10 min to help penetrate the mycolic acid in the cell wall, then rinsed with acid alcohol which washes the carbol fuchsin out of al... Read More

Slaying bacteria with their own weapons

A chemist at Washington University in St. Louis is studying siderophores, iron chelating molecules released by bacteria during an infection, with the thought of using them to design personalized antibiotic therapy that would avoid the rapid evolution of resistance that plagues antibiotic drug di... Read More

Endospore Stain Bacillus cereus

B. cereus was grown on urea agar for 6 days at 37 degrees C to induce spore formation.
The endospore stain was done using malachite green as the primary stain and safranin as counter the stain. Malachite green was applied to the smear and set over a steaming water bath for 10 min (stain was no... Read More

Live/Dead Stain Microscopy

Tannery tanning fluid sample stained with Live/Dead BacLight under UV light. Either 40x or 100x oil immersion. Green bacteria indicate living cells, while Orange bacteria indicate dead cells. Some of the green cells were moving around even after staining! Read More

Starch Agar

Starch agar contains high molecular weight starch molecules (soluable starch). When Iodine is added it reacts with starch to produces a dark brown/purple color. A zone of clearing forms around organisms that produce the exoenzyme amylase after addition of iodine. This plate was incubated for ... Read More

Fluid Thioglycollate Media

Organisms grown in Fluid Thioglycollate Media w/out resazurin dye is a reducing media that uses sodium thioglycollate to chemically combine with dissolved oxygen to deplete the oxygen in the media. All organism except for Neisseria sicca were grown for 48 hours at 37 degrees C. Neisseria sicca i... Read More

Enterobacter aerogenes on MacConkey Agar (Mac)

Streak plate isolation of Enterobacter aerogenes grown on MacConkey agar for 24 hours at 37 degree's. Colonies grow pink due to fermentation of lactose. Read More

MaConkey Agar (Mac)

Organisms grown on MacConkey Agar at 37 degrees for 24 hours.
-Important Ingredients: crystal violet, bile salts, neutral red (color indicator), lactose
-Differential: used to identify and isolate lactose fermenting G- enteric bacteria mainly Enterobacteriaceae. Strong lactose fermentation pr... Read More

Salmonella grown on Salmonella-Shigella (S-S) Agar

The following picture shows the isolated black colonies of Salmonella on Salmonella-Shigella (S-S) Agar. S-S Agar is used as a selective and differential medium for the isolation of Salmonella and some Shigella species. The inclusion of bile salts is to inhibit gram-positive organisms. Ferric ci... Read More

E.coli on MacConkey Agar (Mac)

Streak plate isolation of E. coli on MacConkey Agar grown for 24 hrs at 37 degrees. E. coli demonstrates strong lactose fermentation indicated by the bright pink halo, bile precipitant around the colonies, and pink colony growth. Read More

ASM GM 2014 - Where Pathogens Can Linger on Airplanes

Many air travelers are concerned about the risks of catching a disease from other passengers given the long time spent in crowded air cabins. New research shows disease-causing bacteria can linger on surfaces commonly found in airplane cabins for days, even up to a week. Participants discuss ... Read More

Unknown Agar Contaminate

Unknown contaminant found on a TSA plate after being in the refrigerator for 1 month. Organism had grown throughout the media, was pale yellow and mucoid. Read More

Mannitol Salt Agar (MSA)

Mannitol Salt Agar (MSA)
•Important Ingredients: Phenol red, mannitol (sugar), 7.5% NaCl
•Differential: between pathogenic S. aureus and S. epidermidis
•Selective: NaCl inhibits non-halophilic organisms. Organism that can grow are halophilic.
•Mannitol Fermentors: fermentation of acid cau... Read More

Mannitol Salt Agar (MSA)

Mannitol Salt Agar (MSA)
•Important Ingredients: Phenol red, mannitol (sugar), 7.5% NaCl
•Differential: between pathogenic S. aureus and S. epidermidis
•Selective: NaCl inhibits non-halophilic organisms. Organism that can grow are halophilic.
•Mannitol Fermentors: fermentation of acid cau... Read More

E. coli colonies on Eosin Methylene Blue agar plate

Isolates colonies of E. coli with distinct green metallic sheen on EMB agar plate. Culture isolated from drinking water sample Read More

Bacitracin test on Streptococcus pyogenes

Bacitracin test done on a lawn of Streptococcus pyogenes grown on blood agar. The zone of inhibition around the bacitracin disc, approx 14mm measuring the entire length of the zone, indicates sensitivity. The zone of inhibition is red because the red blood cells did not lyse. Grown for 24 hr... Read More

Streptococcus mitis on blood agar

Growth of Streptococcus mitis on blood agar demonstrating alpha hemolysis seen as a greenish color around the growing colonies due to a reduction of the hemoglobin to methemoglobin in the surrounding agar. Image taken using transmitted light. Read More

Freshman Biology Creative Projects!

I have found that students become involved, energized, and enthusiastic when I give them opportunities to explore topics in my classes using their own creative approaches and interests. So this semester, in my Biology 111 course at the University of Puget Sound, I found that students explored f... Read More

Where Biology and Art Work Together in the Classroom

In this blog entry, I describe how working with the artist Katie McKissick ("Beatrice the Biologist") helped improve my freshman biology course. The intersection of biology and art benefits both! Read More

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